Radioreception



Oct. 16, 1923. 1,471,165

L. L. lSRAEL NOW BY JUDICIAL CHANGE OF NAME L. L. JONES A RADIORBCEPTIONFiled July 19. 1920 2 Shoots-Shoot 2 LesierL ,lrael, now by judicialchange afruzme,

Lesier Z Jbnes.

4 A'ITORNEY Patented Oct. 16, 1923.

UNITED STATES PATENT OFFICE.

LESTER L. ISRAEL (NOW BY JUDICIAL CHANGE OF NAME LESTER L. J ONES),

OF NEW YORK, N. Y.

RADIORECEPTION.

Application filed July 19, 1920. Serial No. 397,167.

To all whom it may concern:

Be it known that I, LESTER L. ISRAEL, now by judicial change of nameLESTER L. JONES, a citizen of the United States, resid- 6 ing at NewYork city, in the county of New York and State of New York, haveinvented certain new and useful Improvements in Radioreception, fullydescribed and represented in the following specification and the 10accompanying drawings, forming a part of the same.

This invention relates to a method and apparatus or system for thereception of radio signals. The invention aims to pro- 16 vide areceiving system whereby radio sig nals of low damping, and especlallycontinuous waves, may be efiiciently received with the exclusion ofdisturbances of all kinds resulting from waves or pulses of relatively20 high damping, or from waves differing in frequency from the signalwaves. A further object of the invention is to provide a receivingsystem in which sustained wave signals are received in an indicatoroperable by audible frequency current produced by the periodicinterruption method and which has the advantage that the whole availablesignal energy is absorbed from the wave field for operating theindicator. A further object of the invention is to provide a unilateralloop receiver which in addition to the usual advantage of directionalelimination of such a receiver, shall have the property of substantiallyeliminating disturbances re- 36 sultingfrom waves coming from directionsfrom which the desired signal waves reach the receiver.

lVith these objects in view, the invention comprises a method whereintwo receivin 40 antennas, or absorbing means, are utilize which aredesigned to receive substantially equal amounts of wave energy of highdamping or of frequency substantially difl'erent from the signalfrequency, and greatly unequal amounts of signal energy of low damping,and wherein the currents produced by the energy absorbed in the twoantennas are separately rectified and thereafter combined in oppositionfor operating the indicating means. The currents resulting from energyabsorbed from waves of high dam ing, and from waves of a frequency sustantially diflerent from the signal frequency, are thus caused toneutralize each other in the indicating circuit, while a signal currentis produced in the indicating circuit by the absorbed signal wave energyof low damping and operates the indicating device free from disturbance.The two receiving antennas should be electrically alike should have lowand equal dampings, an

should be in close proximity and electrically and magnetically decoupledone from the other. Loop antennas are best used because of the greaterdifiiculty of decoupling open antennas. The loop antennas should bothpoint in the same direction, and should most desirably be symmetricallyplaced with respect to surrounding objects. For convenience in adjustingthe setting of the loops it is desirable to use loops of fairly smalldimensions.

In operation, the antenna through which the signal waves are to bereceived is tuned closely to thesignal wave, and the other antenna isslightly d'etuned from the signal wave length. Such detuning shouldbe'sufficient to cause only a relatively small amount of signal energyto be absorbed by the detuned antenna, preferably to a wave length 1% or2% shorter or longer than the signal wave length. The receiving antennaswill then absorb greatly unequal amounts of signal energy of lowdamping, but will absorb substantially equal amounts of wave energy ofhigh damping or of a frequency substantially difi'erent from the signalfrequency. In receiving spark signals, one antenna may be permanently sodetuned while the. other serves alone for receiving the signal waves.For continuous wave reception by the periodic interrl'lption method, Icause, according to my present invention, the two receiving antennastobe periodically in tune and slightly out of tune with the signal wave,one being detuned while the other is tuned to the signal wave, and theperiodic tuning and detuning being at an audible frequency. In this waythe signal currents are caused to alternate first in one loop and thenin the other, and the whole available signal E. M. F. in the region ofthe antennas is absorbed, while the static, being more of a pulse ordamped excitation, will excite both loops the same, and the loops beingadjusted to have equal decrements in the wave length range of variationunder the action of the detuning means, the envelope of the staticoscillations will be nearly identical.

The invention may be carried out with the use of unilateral loops byusing an open antenna exciter for each loop, either aperiodic openantennas, or tuned open antennas which are detuned synchronously withthe respective loops with which they are associated.

A full understanding of the invention and the various features thereofcan best be given by a detailed description in connection withdiagrammatic representations of illustrative systems embodying and forpracticing the invention, and such a description will now be given inconnection with the accompanying drawings, in which:

Fig. 1' is a diagrammatic representation of a simple loop receivingsystem embodying and for practicing certain features of the invention;

Fig. 2 is a similar diagram of a unilateral loop receiving systemaccording to the invention;

Figs. 3 and 3 are diagrams illustrating the envelopes of the rectifiedcurrents from the two loop receiving circuits; and

Fig. 4 is a view illustrating a way of mounting the loops and co-acting'circuits and apparatus. 1

Referring first to Fig. 1, the apparatus shown comprises two loopantennas A and B of the same electrical characteristics, the loopcircuits being provided with the usual balancing condensers 10 and 11,and variable tuning condensers 12 and 13. The loops should have minimumcoupling with each other, which condition may be obtained by having themmounted not too close together and by providing static shields 15, 16and 17 and an adjustable decoupler 18 having small coils a and bconnected to the respective loop circuits.

The antenna circuits each feed into a rectifying circuit, C and Drespectively. The rectifying circuits may be of any suitable character.Fig. 1 shows simple electron tube or audion circuits each having inaddition to the secondary of the radio frequency transformer by which itis coupled to one of the antenna circuits, a coil forming the primary ofan audiofrequency transformer by which the rectifying circuit is coupledto an indicating circuit E common to both rectifying circuits andprovided with an audio frequency indicating device 20, usuall atelephone receiver as shown.

The loop circuits should be constructed to have low and equal dampings,and for sustained wave reception and for the most eflicient eliminationof static and avoidance of disturbance resulting from other highlydamped waves and interference by waves of low damping but of widelydifferent wave length from the signal wave, the two loop circuits aretuned to the signal wave, as by means of the variable condensers 12 and13 in the arrangement shown, and are periodically and alternatelyslightly detuned by means of periodic detuning means such as means forperiodically varying the capacity or inductance of the circuits. In thear-. rangement shown in Fig. 1 there is provided a tone condenser deviceF comprising condenser elements 22 and 23 connected in the circuits ofthe loops A and B respec tively, and a rotor carrying a plurality ofcondenser elements 24. This device is adjusted and operated to detunethe loops by' 1% or 2% alternatel at a suitable audio frequency, mostdesira 1y of the order of 300 to 1000 cycles, and in-such manner thateach loop is detuned for approximately one-half the time or slightlymore, and that when one loop is in tune the other is out of tune. Signalcurrents resulting from signal waves absorbed by the loops will thusalternate first in one loop and then in the other, and since the twoloops are always out of tune with each other, their reaction on eachother and on the signal wave field is negligible and the whole availablesignal energy in the region of the loops is absorbed. The static,however, being more of a pulse or damped excitation, will not beaffected by the periodic detuning of the loop circuits, but will exciteboth loops equally even though they are relatively detuned, and theloops being adjusted to have equal decrements in the wave length rangeof variation under the action of the detuning means, the envelopes ofthe static oscillations will be nearly identical; and. the same is truein the case of waves of low dampin out of widely different wave lengthfrom the signal wave, since the forced oscillations of such interferingwave frequency will have practically the same amplitude in'the twoantennas.

The loop circuit currents being impressed on the rectifying circuits Cand'D, the signal currents give rise to rectified audio frequencycurrents as indicated by heavy lines in Figs. 3 and 3 the currents inthe two circuits being opposite in phase, and the static or otherdisturbing currents give rise to rectified currents as indicated bylight lines in Figs. 3" and 3" which are in phase. These rectifiedcurrents produced in the rectifying circuits being applied to theindicating circuit. are comoined in opposition in the indicating circuitand produce opposing E. M. Fs in the telephone or other detectingdevice. The static and other disturbing E. M. F.s will approximatelycounterbalance each other and have no effect on the telephone, and thesignal E. M. F.s will produce an alternating current which may be madeto be of approximately sinusoidal having the loop form. The indicatorcircuit is best when of fairly low damping and resonant to the tonecondenser frequency. This circuit may then be loosely coupled with therectifying circuits so as to minimize reaction between these circuits.

Any suitable amplifying means adapted for amplifying without distortionof ampli tudes may be provided in the system for amplifying the currentseither before or af ter rectification, and if desired, amplification maytake place after the separately rectified currents have been combined.

Fig. 2 shows diagrammatically a unilateral loop receivin system which issimilar to that shown in antennas A and B of the same electricalcharacteristics, the circuits of which are decoupled b means of staticshields 15, 16 and 17 an decoupling coils a and b, and in circuitscoupled to rectifying circuits C and D respectively, which rectifyingcircuits are in turn both coupled to a common indicating circuit E. Asin Fig. 1, the rectifying circuits are inductively coupled to therespective loop circuits and to the common indicating circuit; but theaudio frequency transformers coupling the rectifying circuits to theindicating circuit are, however, in this figure shown as iron coretransformers, and the rectifying circuits are provided with crystalrectifiers.

Coupled to each loop antenna is an open antenna, A and B respectively,for limiting the directional receptivity of the loops. Aperiodic openantenna exciters may be used with fairly good results,'but most desirabltuned open antennas are employed, each such antenna being as nearly aspossible in tune with its corresponding loop antenna, and when the loopantennas are detuned alternately the associated open attennasare detunedcorrespondingly and synchronously with the loops with which they areassoci ated. Such periodic detuning may be effected by any suitablemeans. In Fig. 2 there is shown means for elfectin such detuning byvarying the inductance of t e antenna circuits, such means comprisingsmall inductance elements or coils and 31 connected in the circuits ofthe loops A and B respectively, and similar coils 32 and 33 connected inthe open antenna circuits A and B respectively, and rotors 34 and 35each carrying a plurality of inductance elements 36. The rotor 34 isoperated to detune the loop circuit A and its associated open antennacircuit A simultaneously and periodically at a suitable audio frequency,and the rotor is operated to detune the loop circult B and itsassociated open antenna circuit B simultaneously and periodically at thesame audio frequency, and the two rotors operate in synchronism todetune the respective pairs of circuits, A, A and B, B alternately ig. 1in having two loopnal and in such manner that each pair of cir' cuits isdetuned for approximately one-half the time or slightly more, and thatwhen one pair is in tune the other is out of tune. The detuning means isdesirably adjusted to detune the antenna circuits by 1% or 2%.

The tone inductance devices may be connected in any suitable manner inseries or in (parallel with the respective loops so as to etune theloops by the inductance variation, but are best connected in series withthe transformer coils and at their midpoints as shown. The open antennasmight be coupled inductively with the loop antennas, but I find it mostdesirable tojemploy capacitive coupling through connection through thebalancing condensers 10 and 11 of the loop circuits as shown in Fig. 2,and in this case the energy receptivity of the open antenna should befrom one to five times that of the loop. This way of coupling has theadvantage of being more constant on different wave lengths and of givingonly one degree of freedom to the loop andopen antenna system.

receiving'system or apparatus such as shown in Fig. 2 will operate toreceive sigwaves and to exclude disturbances in the same way as theapparatus of Fig. 1, the open antenna exciters serving the usual purposeof limiting the directional receptivity of the loop, and currentsresulting from energy absorbed by these open autennas from waves of highdamping and from waves of a frequency substantially different from thesignal frequency. being caused to neutralize each other in theindieating circuit in the manner already explained. The open antennasshould, as in the case of the loo antennas, be electrically alike, andshould have equal dampings. The dampin of the system will be nearly aslow as t e damping of the loop even though the open antennas have a veryhigh damping.

As stated, the invention-is effective not only in avoiding disturbancedue to static and other waves of high damping, but also in eliminatinginterference due to waves of low damping but of widely different wavelength from the signal wave, and this is so even when such interferingwaves are from nearby high power transmitters. This elimination is due,I believe, to the fact that the forced oscillations of interfering wavefrequency have practically the same amplitude in the two antennas, sothat their rectified currents when combined in opposition in theindicating circuit balance. As the interfering wave approaches thefrequency of the signal wave the elimination becomes less and less, butsuch waves which would not otherwise be eliminated may be eliminated byadjusting the antennas so that they detune on opposite sides of theresonant point for the signal wave, and by loosening the couplingbetween the indicating circuit and for best results be symmetricallyplaced with respect to the surrounding objects. Otherwise the twoantennas willnot be equally excited bythe static impulses and otherforms of electromagnetic disturbance. This is principally a matter ofproper adjustment 1 of the angle between the axes of the loops and thes1gnal wave direction to symmetry withth'e surrounding objects. In orderthat the desired adjustment may be readily made, the loops aregmostdesirably mounted on a rotatable su shown by 1g. A in which the loopsare mounted on a platform 40 Whichis rotatable about an upright axis andon which the other elements-of the receiving system, represented in thisfigure by the casing 41, are also most desirably mounted.

In the preceding description and explanation of the invention I havesought to point out the features andconditions necessary for bestresults in the use'of my invention, and

more particularly in the illustrative systems shown in the drawings andto which the description more especially applies. I may further statethat in order to make the invention most effective under all conditions,the two antennas should be efiectively shielded from excitation byso-called contact static, as by the use of static shields, because thisform of excitation is not equally applied to both antennas; that therectifying means used should be such as do not change the damping of theantennas when oscillation currents of different amplitudes are beingrectified; that the oscillatory circuits should be constructed so as tohave no change of damping over the range of wave length variation used;and that the two antennas should have equal radiation receptivity,especially to waves or pulses of high damping.

What is claimed is:

1. In the art of radio reception, the method of receiving signals whichcomprises absorbing electro-magnetic energy from the atmosphere in twoantennas having low damping and approximately the same electricalcharacteristics, setting the antennas in close proximity and to receivert. Such an'arrangement is from the same direction, preventing transferof energy between the antennas, tuning one antenna to the signal waveand slightly detuning the other therefrom, rectifying the currentsgeneratedin each of said antennas, combining in opposition forces due tothe rectified currents, and operating an indicatin means by theresultant force.

2. In the art of radio communication, the method of receiving signalshich comprises absorbing electromagnetic energy from the atmosphere intwo receiving antennas, pericdically and alternately tuning saidreceiving antennas to and slightly detuning them from the signal wave,rectifying the currents ori -'nating in each of the antenna systems, ancombining the rectified currents in opposition in an indicating circuit.

3. In the art of radio communication, the method of receiving signalswhich comprises absorbing electro-magnetic energy from the atmosphere intwo receiving antennas, periodically and alternately tuning saidreceiving antennas to and slightly detuning them from the signal wave,said periodic tuning ,and;detuning being at audio frequency, rectify1ngthe currents originating in each of detuning each antenna with respectto the frequency of the signal wave, one antenna being detuned while theother is tuned to the signal wave and the periodic tuning and detuningbeing at an audible frequency, means for rectifying oscillatory currentsproducedby the energy absorbed by each of said antennas, and means forcombining the rectified currents in opposition.

5. A radio receiving system, comprising in combination two receivingantennas designed to absorb substantiallyequal amounts of wave energy ofhigh damping and unequal amounts of signal wave energy of low damping,means for periodically tuning and slightly detuning each antenna withrespect to the frequency of the signal wave, one antenna being detunedwhile the other is tuned to the signal wave and the periodic tuning anddetuning being at an audible frequency, means for rectifying oscillatorycurrents produced by the energy absorbed by each of said antennas, meansfor combining in opposition forces due to the rectified currents, andindicating means operated by the resultant force.

6. A radio receiving system, comprising in combination two receivingantennas designed to absorb substantially equal amounts of wave energyof high damping and unequal amounts of signal wave energy of lowdamping, means for periodically tuning and III slightly detuning eachantenna with respect to the frequency of the signal wave, one antennabeing detuned while the other is tuned to the signal wave and theperiodic tuning and detuning being at an audible frequency, means forrectifying oscillatory currents produced by the energy absorbed by eachof said antennas, and means for applying the rectified currents inopposition to a common indicating circuit.

radio receiving two receivin antennas and means ar electrically andmagnetically decoupling said antennas, said antennas having similardirectional receiving characteristics and being arranged for the samedirectional reception and one bein tuned to the signal wave and theother being slightly detuned therefrom in combination with means forrectifying oscillatory currents produced by the energy absorbed by eachof said antennas, and means for combining the rectified currents inopposition.

8. A radio receiving system, comprising two receiving antennas in closeproximity and means for electrically and magnetically decoupling saidantennas, said antennas having low damping radiation receptivity and thesame electri cal characteristics except that one is tuned to the signalwave and the other is slightl detuned therefrom, in combination witmeans for rectifying oscillatory currents produced by the energyabsorbed by each of said antennas, and means for combining the rectifiedcurrents in opposition.

9. A radio receiving system, comprising two receiving antennas in closeproximity, means for electrically and magnetically decoupling saidantennas means for periodically tuning and slightly detuning eachantenna with respect to the frequency of the signal wave, one antennabeing detuned while the other is tuned to the signal wave and theperiodic tuning and detuning being at an audible frequency, means forseparately rectifying the oscillatory currents originating in each ofthe antenna circuits, and means for applying the rectified currents inopposition to a common indicating circuit, whereb the electro-motiveforces of the two recti ed currents counterbalance each other when saidcurrents are equal in amplitude and phase.

10. A radio receiving system, comprising in combination two receivingantennas in close proximity and electrically and magnetically decoupledone from the other, means for periodically tuning and slightly detuningeach antenna with respect to the frequency of the signal wave, oneantenna being detuned while the other is tuned to the signal wave andthe periodic tuning and detuning being at an audible fresystem,comprising 1n close proximity b and directionally equal fi quency, tworectifying circuits one fed from each of the antenna circuits, and acommon indicating circuit to which currents from said rectifyingcircuits are applied in opposition.

11. A radio receiving system, comprising in combination two like loopantennas in 12. A radio rece1ving system, comprising in combination twolike loop antennas in means for periodically tunin and slightly detunrngeach antenna witfi respect to the frequency of the si al wave, oneantenna being detuned whi e the other tuned to the signal wave, and theperiodic tuning and detuning. being at an audible frequency, means forseparately rectifying oscillatory currents originating in each of theantenna terbalance each other when said currents are equal in amplitudeand phase.

13. A radio receiving system, comprising in combinationtwo likeunilateral antennas for electrically and magnetically decoupling saidantennas, means for rectifying oscillatory currents produced by theenergy absorbed by each of said antennas, and means for combining inopposition forces due to the rectified currents.

14. A radio receiving system, comprising in combination two likeunilateral antenna systems each comprising a tuned loop antenna of lowdamping and a tuned open antenna of high dampingv capacitively coupledthereto, said antenna systems belng set for reception from the samedirection, means for electrically and magnetically decoupling saidantennas, means for rectifying oscillatory currents produced by theenergy absorbed by each of said antennas, and means for combining inopposition forces due to the rectified currents.

15. A unilateral receiving antenna system comprising a tuned loopantenna of low damping and a tuned open antenna of high dampingcapacitively coupled thereto.

16. A radio receiving system, comprising two loop antennas mounted inspaced relation on a support which i rotatable about an upright axis.

17. A radio receiving system, comprising two loop antennas mounted on asupport which is rotatable about an upright axis, each loop antennabeing mounted to rotate about its own axis.

18. A radio receiving system, comprising two loop antennas mounted on arotatable support, means for electrically and magneticall decouplingsaid antennas, tuning means or said loops, means for rectifyingoscillatory currents produced by the energy absorbed by each of saidantennas, and

means for combini the rectified currents in opposition, all sai meanbeing mounted on saidrotatable support. 1

In testimony whereof I have hereunto 1 set my hand in the presence oftwo sub scribing witnesses.

LESTER L. ISRAEL. Witnesses Erma. J omms, A. L. Kmm

